Re: Short address

That's not always true, because sometimes a postcode can cover more than one street. So the house number isn't necesarily unique within a postcode - you do need the street name as well in order to be certain.

Mark

I take exception to the "So".

Although a postcode might cover more than one street, this does not necessarily imply that a house-number/postcode pair might fail to identify a house uniquely.

For instance, a particular postcode might cover 20 houses which lie in

3 different streets. I put it to you that the boffins who allocated the postcodes will have ensured that no two of these 20 houses share the same house number.

The sort of thing I'm thinking about is that TT1 2XY might cover even numbers between 20 and 50 of Main Street, Toytown, and also all 6 houses (numbered 1 to 6) in The Lane, Toytown, being a small cul-de-sac off Main Street, on its even-numbers side, somewhere along the range 20-50. So the only numbers which can be paired with TT1 2XY are 1,2,3,4,5,6,20,22,24,...,48,50, and clearly any of the first 6 must be in The Lane, and any of the rest must be on Main Street.

Suppose that next to each other are 1 Old Cottage, 2 Old Cottage, 1 New Cottage, 2 New Cottage all in the same road and post code. Perhaps an exception to the OPs original point - but I have been there. It upsets the computer systems that use post codes to get address details. Anything that required a credit check - say a moblie phone contract took longer.

There was also the issue of companies that would not enter the data properly. I used to live at Number 1 Long Road. (Really number 1, first house in the road) about a mile away and on the other side were 1 and 2 Some Cottage. I often got mail for 1 Some cottage, usually because the local sorting office didn't read the address properly, but sometimes because some company had not done the data entry work carefully enough. On one occasion the local postie was quite put out because I would not sign for a recorded delivery letter that was not addressed to me. On other occasions I would put correctly addressed - but wrongly delivered mail back in the nearest postbox - only to get it back again 2 hours later! This was 6 years ago and I don't think we have such a fast service now.

No, they won't. Postcodes are more likely to cover more than one street when at least one of the streets is very short, so there's quite a strong likelihood of duplicate numbers in such cases.

In any case, postcodes are allocated for one purpose only: To assist with delivering the post. There are no other considerations taken into account; avoiding duplicate numbers is certainly not part of the criteria.

But if TT1 2XY covers houses 1 to 20 of Main Street, and The Lane is a cul-de-sac in between 5 and 7, then all six houses in The Lane will have the same postcode and house number as a house in Main Street.

Mark

I remember reading some Royal Mail documentation about 20 years ago which said that they were working towards the principle that a postcode would cover only a single street. However, the favoured design of modern developments has strongly militated against that little desideratum -- now you tend to get one road snaking through the whole development with lots of little cul-de-sacs off it at intervals, each with its own name and numbers. There's no way each of these cul-de-sacs is going to warrant its own postcode, so the net result is lots of numbering clashes within the postcode, resolved only by including the streetname.

Matti

At 10:24:01 on 29/09/2007, Tiddy Ogg delighted uk.finance by announcing:

My mum's house can be identified solely by the postcode.

"Mark Goodge" wrote

Can you give any examples of postcodes with duplicate numbers?

You can try looking here:-

[Watch for wordwrap, and notice that you can just enter a postcode (alone), and it will then list all entries under that postcode.]

Naturally, but the thrust of my remark was that in that case they would have allocated the postcode differently. For example, they might use one code for all six numbers in The Lane and for odds on Main Street from 7 upwards, and lump in 1/3/5 Main Street with the evens on Main Street from 2 upwards, which have a different code. Now, if there's an additional side lane (perhaps "The Mews") between 6 and 8, that wouldn't work, but other solutions would be possible instead, such as giving The Lane or The Mews a code all to itself.

The purpose of the postcode is to make mail easier to sort and to deliver, and it's obvious that if all they then needed to identify any premises uniquely is one more item of information, namely the house number, then that would further the same aim.

Mind you, there is still some way to go. There still exist streets on which the houses don't have numbers yet, and are still identified only by name. Check out FK15 0DP as an example.

A single postcode covers a set of adjacent premises in such a way that, having opened the bundle for AA1 1AA, the postman can then deliver all of it before needing to open the bundle for AA1 1AB, and, as far as possible, can avoid the necessity of retracing his steps in order to deliver AA1 1AB after having delivered AA1 1AA. That's why it's often the case that two sides of the same street have different postcodes: the postie walks up one side delivering one set and then back down the other side delivering the other. So if there's a short sidestreet of no more than a few houses off a longer street, then it makes sense for the entirety of that sidestreet to be the same postcode as the side of the longer street onto which it abuts.

That's obviously not always possible; determining the optimal route for a postman on foot is similar to the travelling salesman problem and sometimes there's no alternative to retracing your steps. But the overriding principle is that of efficiency in delivering the mail, not in efficiency of house number allocation :-)

There's no requirement to have house numbers at all, and the Post Office don't have any say in allocating them (which is another reason why the PO can't ensure that there are no duplicates within a postcode).

To give an example of a different situation, the office block I work in has no number, just a name. The building as a whole has a single postcode, but it contains four separate premises, one of which has a floor sub-let to another tenant. So, in this case, the name of the building is superfluous as the postcode alone uniquely identifies it, but the first line of the address (being the business name) needs to be given in full in order to disambiguate the code. This is consistent with the general principle which also applies to residential addresses: The minimal postal address consists of the first line and the postcode. Everything in between the first line and the postcode is superflous and can be ommitted if necessary, but lines which are required (the first and last) cannot be further subdivided and parts omitted without risk of duplication.

Mark

In message , Alex writes

Lucky Mum! Must be a big house or miles form anywhere.

At 22:34:23 on 03/10/2007, John Boyle delighted uk.finance by announcing:

Try 'old'.